PROJECT SUMMARY (Pilot/Feasibility Core) The objective of the BBDC Pilot/Feasibility Core (PFC) is to build on our experience in years 1-5 to continue a solicitation, review, funding, and reporting of pilot studies from both inside and outside the BBDC investigator community for research projects that leverage the BBDC infrastructure and data. The ultimate goal for these pilot projects is to advance the mission of the BBDC, especially as it relates to clinical trial readiness in Osteogenesis Imperfecta as well as more broadly on rare bone diseases. In years 1-5, two pilots were proposed in the prior application and both pilot studies have been completed. These produced data that informed the design of the longitudinal study of OI (Project 1) specifically in the area of anxiety and pain interference in OI), and that led to two publications on the topic of PROMIS and patient engagement in research. In addition, we also developed a process for soliciting, reviewing, and funding of new pilot studies. This resulted in submission of 17 proposals from both inside and outside of the BBDC. We ultimately funded on project on collagen X biomarker measurement which supported the scientific premise of the current Project 3 proposal on longitudinal biomarker study of growth in OI. We propose to extend and improve on this pilot mechanism by broadly soliciting applications from a wide community of OI and bone health researchers. We will continue a review process that is in the NIH format while emphasizing projects that support the BBDC mission, leverage the BBDC infrastructure and data, and advance clinical trial readiness.